Alternating-current motor and starting-switch.



M. MILGH.

PATENTED MAY 1, 1906.

ALTERNATING CURRENT MOTOR AND STARTING SWITCH.

APPLIGATION FILED SEPT.9,1904.

'Maurice Milch p.

nnirnn snares QFFIQE,

MAURlCE l'llLGl-l, OF SUHENECTADY, NElV YORK, ASSlGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ALTEQNATlilG GURRENT MOTOR AND STARTlNG SWlTCl-L o Application filed September 9. 1904 Serial No. 223538.

To all whom it ma concern/.-

Be it known that I MAnnion MILCH, a sub ject of the King of Hungary, residing at Schenectady, in the county of Schenectady and State of New York, have invented certain new and useful Improvements in Altermating-Current Motors and Starting-Switches,

of wl1 ch the following a specificaton.

, My invent on relates to alternating-cur rent motorsof the commutator type; and its object is to provide a novel form of automatic control for such motors, whereby they are caused to start with the characteristics of a2 repulsionmotor and when up to speed caused to operate with the characteristcs of an induction-motor.

In my former patent, No. 787,305, dated April 1-1, 1905, I have pointed out the fact that the repulsion-motor as heretofore constructed has the characteristics of the d rect- '-cur1 'ent series Inotor that is, it has a maximum torque at starting and the speed 1ncreases with a decrease of loadand that wh; is such a motor is eminently suited for ra .lway work 1t has a serious disadvantage as regards certain other classes of work in that its speed circuiting brushes, so placed on the common ta tor that the motor combines the characteris ticsv of the repulsion-motor with that of the induction-motorthat is, it has a starting Sue a motor with all the brushes permanently short-circuited has a smaller starting torque than the ordinary repulsion-motor, and in a second application, Serial EJ018912 1, filed by me January 15, 1904 I have disclosed an arrangement in which the motoris started as an ordinary repulsion-motor with only one set of brushes short-circuited and in which automatic meansis provided for shorten-cuting the second set of brushes when the motoris up to speed. By means of this arrangement the motor has the full starting torque of the ordinary repulsion-motor, but has its speed definitely limited when the second short-cir- Specification of Letters Patent.

torcgie and its speed has a definite limit;

-i of the same,

of brushes 6 b" and Patented May 1, 1906.

cuit is established. When a polyphase arran ement of brushes is used, the variation. 5 5 in t e voltage at the brushes which are opencircuited at the starting may be utlized for controlling an automatic switch, which short circuits them when the motor is up to speed. In that application I showed a magnet-wind- 6o ing so connected as to have impressed upon it both the voltage induced at the open--circuit ed pair of brushes and a voltage approximately equal thereto at starting, thetwo voltages being opposed to each other. The magnet consequently is notenergized at starting; but as the motor'speeds up and the voltage across theopen-circuited set of brushes decreases the magnet-winding becomes energized and closes a switch, short-circuit'ng the' brushes either directly or through a source of compensating clectromotive force.

My present invention consists in the combinatlon with a motor of the-type clesci'iber in my former applications of an automatic switch, the magnet-winding of which instead than would be possible with the former arrangement, and no current is wasted in the winding while the motor is running.

My invention will best be understood by reference to the accompanying drawings, in

1 which Figure 1, shows diagrammatically an alterhating-current motor provided with an automatic controlling-switch in accordance with my invention, and Fig. 2 shows a modification In 1, A re resents the primary or stator winding, an B represents the secondary or rotor windii: rovided with two sets The first set is permanently short-circuited and-arranged at an angle to-th'e line of magi'etization produced by the primary winding, as in the ordinary repulsion-motor. A second set of brushes 1s connected through a small portion of the 'prilnary winding to'the magnet-coil C of the au tomatic. controllingewitch. l have 1nd1- (rated diagrammatically a construction of the ,switch itself, which is diselosed and fully described in Patent No. 775,501, issued to Ernest Schattner November 22, 190 i. The switch Consists of the pivoted arm D and a loosely-pivoted member E, which normally rests against and is' operated by the arm D when it is moved to open the switch. As the arm D is moved into closed position to engage the stationary contactd'tlie arm E falls into the armature e, carried at,its end, and is brought opposite to the poles of the magnet, on which is wound the coil C. If coil G is energized, the armature E will be restrained and will not follow the arm D to closed position. When coil C is denergized, however, arm E will fall, bringing the contact member F, carried thereby, into engagement with the stationary contacts f.

The operation is then as follows: As soon as arm D comesinto engagement with the contact 61 the circuit of the motor is closed, and the motor starts like an ordinary repulsion-motor. The cross-flux in the motor produced by the rotor-winding induces an electromotive force between the brushes 6 12 which at starting is of considerable magnitude, and this electromotive force energizes coil C, so that arm E is restrained in its open position. The small portion of the fieldwinding A which is included in circuit with the brushes b b may be neglected from con.- sideration at starting on account of its T613: tively small amount as compared with the electromotive forces induced at the brushes b b at starting. As the motor speeds up, however, an electromotive force is induced between these brushes by cutting the primary field, and this second electromotive force opposes that due to transformer action. The resultant electro'motive forces across .the brushes b b consequently fall, decreasing the current-flow through magnet-winding (3.. By

.properly proportioning the strength of the magnet-winding it may be caused to release the arm E at any desired speed of the motor. Arm E will then fall, short-circuitingthe con tact f, which short-circuits the coil C and also short-circuits the brushes b I)? through the small portion of the primary winding included in circuit therewith. This small portion of the primary winding is included in circuit so as to impress upon the brushes a compensating electromotive 'force which improves the power factor of the motor. This source of electromotive force may be left out of circuit, if preferred, and the brushes shortcircuited directly.

It is evident that, as disclosed in my former applications, the motor is changed from one torque characteristic to another when the circuit of the brushes b b is closed. If the circuit of these brushes be closed at the point where the two torque curves cross each other, it is evident that no shock will be produced in the motor. In other words, the winding i C may be designed to release the arm E at a speed at which the torque of the motor is the l same whether the circuit of the brushes b b i is open or closed.

In Fig. 2 I have shown a modification in which the primary winding A is divided into two portions,which are connected first in series and then in parallel by the switch-arm D. This arrangement serves to decrease the current-flow in the motor at starting. The circuit of the'brushes b b is so arranged that the brushes are short-circuited directly instead of throu h a source of compensating electromotive orce, as in Fig. 1. These modifications are evident from the drawings and require no further description. Other arrangements of contacts and other-methods for limiting the starting-current may of course be employed.

I do not desire to limit myself to the particular construction and arrangement of parts shown, but aim in theappended claims to cover, all modifications which are within the scope of my invention.

What I claim as new, and desire to secure by Letters'Patent of the United States, is

1. In an alternating-current motor, a rotorwinding provided with a commutator, commutator-brushes and connections short-circuiting the rotor on a definite line, a startingswitch for the motor having a movable switch member adapted to close the circuit of the rotor-winding on a second line at an angle to the first, and means I or retarding the movement of said switch member.

2. In an alternating-current motor, a rot orwinding provided with a commutator, commutator-brushes and connections short-circuiting the rotor on a definite line, a startingswitch for the motor having a movable switch member adapted to close the circuit of the rotor-winding on a second line at an angle to the first, and an electromagnet connected in shunt to the rotor-winding on said second line and adapted to retard the movement of said switch member.

8. In an alt-ernating-current mot or, arotorwindirg provided with a commutator, comimitator-brushes and connections shortcircuiting the rotoron a definite line, a startingswitch for the motor having a movable switch member adapted to close the circuit of the rotor-winding on a second line at an angle to the first, and means for arresting the movement of the switch member until the potential of said rotor-wilt ding on said second line falls to a predetermined value.

4. In an alternating-current motor, arotorwinding provided with a commutator, com mutator-brushes and connections short-(in switch adapted to close the primary circuit of the motor, a switch-arm arranged to fall by gravity when said switch is closed and to cuiting the rotor-winding on a definite line, a

close the circuit of the rotor-winding on a second line at an. angle to the first, and means for retardin the fall of said switch-arm.

i 5. In ana ternating-current motor, arotorwindingprovided with a commutator, commutator-brushes and connections short-cir cuiting the rotor-winding on a definite line, a switch adapted to close the primary circuit of the motor, a switch-arm arranged to fall by gravity when said switch is closed and to close-the circuit of the rotor-winding on a second line at an angle to the first, and means for arresting the fall of said switch-arm until the potential of 'the rotor-winding on said second line falls to a predetermined value.

6. In an alternating-current motor, a rotorwinding provided with a commutator, a set of brushes arranged and Connected to shortcircuit the rotor-winding on a line at an angle to the primary field magnetization, a sec ond set of brushes on a line displaced from the first, a starting-switch for the motor havmg a movable switch memberadapted to close the circuit of said second set of brushes,

and. means for retarding the movement of said switch member.

7. In an alternating-current motor, a rotor-' winding provided with a commutator, a set of brushes arranged and connectedto shortcircuit the rotor-winding on a line at an angle to the primary field magnetization, a second .set of brushes on a line displaced from the first, a starting-switch for the motor having ,a movable switch member adapted to close the circuit of said second set of brushes, and

means-for retarding the movement of said switch-arm until the potential between said brushes falls to a predetermined value.

9. In an alternating-current motor, a rotor winding provided with a commutator, a set of brushes arranged and connected to shortcircuit the rotor-winding on a line at an angle to the primary field magnetization, a second set of brushes on a line displaced from the first, a switch adapted to close the primary circuit of said motor, a switch-arm arranged to fall by gravity when said switch is closed and to short-circuit the second set of brushes,

' and a magnet-windingconnected to said second set of brushes and adapted to restrain the movement of said switch-arm.

10. In combination, a repulsion-motor having two sets of commutator-brushes, said sets being displaced from each other by approximately ninety electrical degrees and both sets being displaced from the line of magnetization of the primary member,,connections short-circuiting one set, a starting switch having a movable switch member adapted and arranged to short-circuit the second set, and means for retarding the;

movement of said switch member.

11. In combination, a repulsion-motor having two sets of commutator-brushes, said sets being displaced from each other by approximately ninety electrical degrees and both sets being displaced from the line of magnetization of the primary member, con nections short-circuiting one set, a starting switch having a movable switch member adapted and arranged to short-circuit the second set, and a magnet-winding connected to said second set of brushes and adapted to.

retard the movement of said switch member. 12. In combinatlon, a repulsion motor having two sets of commutator-brushes, said sets being displaced from each other by approximately ninety electrical. degrees and 0th sets being displaced from the line of' magnetization of the primary member, connections short-circuiting one set,-a source of compensatin voltage, a starting-switch having a movab e switch member adapted and arranged to short-circuit the second set through said source, and means for retarding the movement of said switch member.

13. In an alternating-current motor, a rotor-winding provided with a commutator, a set of brushes arranged and connected to short-circuit the rotor-winding ona line at an angle to the primary field magnetization, a second set of brushes on a line displaced from the first, a source of compensatin voltage, a

starting-switch having a movab e memberadapted to close the circuit of said second set of brushes through said source, and means for retarding the movement of said member.

14. In an alternating-current motor, a rotor-winding provided with a commutator, commutator-brushes and connections shortcircuiting the rotor on a definite line, a source of compensating voltage, a starting-switch having a movable member adapted to close the circuit of the rotor-winding through said source on a second line at an angle to the first, and means for retarding the movement of said member.

15. In an alternating-current motor, a stator-winding, a rotor-winding provided with a commutator, commutator-brushes and connections .short-circuiting the rotorwinding on a definite line, astarting-switch for the motor adapted to connect the stator winding in series and in parallel, a switch member adapted to move to closed osition when said switch is closed and to c ose the circuit of the rotor-winding on a second line at an angle to the first, and means for retarding the movement of said switch member.

- 16. In combination, a repulsion-motor "havin two sets of commutator-brushes displace from each other by approximately ninety electrical degrees and both sets being displaced from the line of magnetization of ,the primary member, connections short-cir cuiting one set, a starting-switch for the motor adapted to connect the primary winding of the motor in series and in parallel, a

switch member adapted to move to closed position when said switch is closed and to close the circuit of-the second set of brushes, and means for retarding the movement of said switc'hmember.

17. In an alternating-current motor, a ro-' tor-winding provided with a commutator, commutator-brushes and connections shortcircuiting the rotor on a definite line, a starting-switch for the motor having a movable switch member adapted to-short-circuit the rotor-windin independently of said brushes, and means or retarding the movement of said switch member.

18. In an alternating-current motor, a rotor-winding provided with a commutator,

commutator-brushes and connections shortcircuiting the rotor on a definite line, a starting-switch for the motor having a movable switch member adapted to short-circuit the rotor winding independently of said brushes,

and a magnet-winding in the circuit of the short-circuitthe rotor-winding independently of said brushes, and means for retarding the fall of said switch-arm.

20. In an alternating-current motor, a rotor-winding provided with a commutator, comm1itator-brushes and connections she-T- circuiting the rotor-winding on a definite line, a switch adapted to close the primary circuit of the motor, a switch-arm arranged to circuiting the rotor-winding on a definite line,

aswitch-arm adapted to close the primary circuit of the motor, a second switch-arm operatwely connected to the first and adapted to follow the first when the first arm is closed and to short-circuit the rotor-winding independently of said brushes, and means for retarding the movement of said second switcharm.

22. In an alternating-current motor, a rotor-winding rovided with a commutator, commutatorrushes and connections shortcircuiting the rotor-winding on a definite line, a switch-arm adapted to close the primary circuit of the motor, a second switch-arm operatively connected to the first and adapted to follow the first when the first arm is closed and to short-circuit the rotor-winding inde endently of said brushes; and a magnetwin ingincircuit with the motor arranged to retard the movement of said second switcharm. 

